1. Field of the Invention
The present invention relates to a tunable resonator and a tunable filter. More particularly, the present invention is directed to a tunable resonator and a tunable filter, of which the length of the resonator may be switchably adjusted to allow switching between a plurality of frequency bands.
2. Description of the Related Art
The development of mobile communication and the advent of the Internet have prompted the installation of communication modules in a large number of products. These modules may employ filters that need to satisfy the size and performance demands, for example, combline filters.
FIG. 1 is a diagram showing the configuration of a conventional combline filter 10. The combline filter 10 of FIG. 1 comprises microstrips 11 and 21, one end of each of which is connected directly to a ground, and an opposite end of each of which is connected to the ground via a capacitor.
FIG. 2 is a diagram showing a conventional multi-band front end module (FEM). In FIG. 2, the multi-band FEM includes filters required for each respective band. The multi-band FEM is implemented in such a manner to select a filter for outputting a band required according to a switching operation. However, since such multi-band FEM needs to include as many filters as there are required bands, it is difficult to achieve compactness. Additionally, a large number of microstrips need to be disposed on a substrate in order to form the multi-band FEM using the combline filter, resulting in the increased cost and size of the multi-band FEM.